CMB Polarization from the South Pole: BICEP1, BICEP2, and Keck - PowerPoint PPT Presentation

CMB Polarization from the South Pole: BICEP1, BICEP2, and Keck Array Immanuel Buder for the BICEP1, BICEP2, and Keck Array Collaborations Harvard-Smithsonian Center for Astrophysics ibuder@cfa.harvard.edu CMB2013 Okinawa, Japan 2013-06-10

We need B-mode polarization measurements to go deeper on r ● SPT+WMAP7+BAO+H 0 : r < 0.11 (Story et al., 2012) ● Planck+WMAP (pol.): r < 0.12 (Planck Collaboration XXII, 2013) ● Theoretical limit from sample variance for CMB temperature measurements: r < 0.1 (Knox & Turner, 1994)

We Have the Tools to Reach r = 0.01 ● Statistical power (BICEP2 + Keck Array + BICEP3 + …) ● Systematic control in analysis (being demonstrated in BICEP1 3-year analysis)

Outline of This Talk ● BICEP and Keck Program Overview ● BICEP1 3-year Results ● BICEP2 Analysis Status ● Keck Array Status and Plans ● Conclusion

Overview of BICEP1, BICEP2, and Keck Array ● All designed for measuring ell ~ 100 B-mode polarization ● All observe low-foreground field from South Pole ● All have cold refracting telescopes: 26-cm aperture (far field is close!) ● All have boresight rotation ● All have absorptive co-moving forebaffles and stationary reflective ground shields

BICEP1, BICEP2, and Keck Collaborators California Institute of Technology Harvard University JPL KIPAC Stanford University University of Minnesota Case Western Reserve University NIST University of British Columbia University of Toronto University of Chicago UCSD Photo from Zak Staniszewski Wales Cardiff CEA Grenoble Thanks to National Science Foundation, W. M. Keck Foundation.

BICEP1 ● Observed 2006—2008 ● Polarization-sensitive NTD bolometers ● Feed-horn coupled ● 100/150 GHz dual-frequency focal plane ● First results in 2009 (Chiang et al.) ● Systematic error level at r ~ 0.1 (Takahashi et al.) ● Results in this talk based on 3- year data

BICEP2 Scaled Up # of Detectors ● Observed 2010—2012 ● Planar slot antenna coupled TES ● 256 dual-polarization pixels @ 150 GHz ● Time-domain SQUID mux (x33) ● 10 times faster mapping speed than BICEP1

Keck Array = 5 BICEP2's ● Switch to pulse tube coolers to pack 5 BICEP2-style telescopes on the DASI mount ● Currently all at 150 GHz, but plans include 100 and 220 GHz receivers in future ● Observations 2011—2016 ●

BICEP1 3-year Results ● 3-year maps and sensitivity ● Analysis improvements since Chiang et al. – Bandpower window function calculation – Likelihood model for bandpowers and r – Deprojection of beam systematic errors ● Power spectrum and r limit

BICEP1 3-year maps 5 BICEP1 3-year 150-GHz μK polarization E-modes sensitivity: 500 nK-deg. for effective area -5 203 deg. 2 -50 NET: 54 B-modes uK*sqrt(s) Dec (deg.) -70 -50 50 RA (deg.) Maps from Colin Bischoff

More accurate bandpower window function calculation ● Chiang et al. method included only the mask ● 3-year method incorporates filter and beam – Higher ell resolution simulations to capture change of filter suppression within each bin – Iteratively solve for filter suppression ● Doubles stat. error for lowest ell bin Chiang et al. 3-year Bandpower Window Function ell 150 0

Data release includes improved likelihood models ● For r make quadratic Direct simulation-based estimator and likelihood from scaling r = 0.1 simulations and adding noise simulate at each r value ● For bandpowers, use Hamimeche & Lewis (2008) approximation Offset lognormal has more bias and scatter Maximum ● Replaces Bond, Likelihood Jaffe, Knox (2000) “offset lognormal” (OLN) approximation Quadratic Estimator

Deprojection of Beam Systematic Effects Reduced Error A-B gain mismatch ● Make template map of CMB systematic error reduced temperature and its spatial derivatives ● Subtract the projection of these templates on the real timestream data ● Suppressed the (previously) largest systematic error by ~ 10 4 in power 6 types of beam imperfections can be deprojected—for BICEP1 only (a) is necessary (Aikin et al., 2013 in prep.)

Deprojection of Beam Systematic Effects Reduced Error A-B gain mismatch ● Make template map of CMB systematic error reduced temperature and its spatial derivatives ● Subtract the projection of these templates on the real timestream data from Takahashi et al. (2010) ● Suppressed the (previously) largest systematic error by ~ 10 4 in power 6 types of beam imperfections can be deprojected—for BICEP1 only (a) is necessary (Aikin et al., 2013 in prep.)

BICEP1 Did Not Find B Modes BICEP1 BB Power in CMB Polarization with r = 0.1 model tensor- to- scalar ratio Inset region r < 0.70 (95% C.L.) Angular Scale (Barkats et al. 2013, in prep)

We added 50% more data. Why didn't the upper limit improve more? ● Additional data Chiang et al. found r < 0.72 (95%C.L.) fluctuated up (within statistical prediction) ● Previous bandpower window function approximation OLN (Chiang et al.) underestimated first bin uncertainty ● Chiang et al. got a lucky fluctuation of the OLN scatter

BICEP2 Analysis Status ● Map and sensitivity: 16 uK*sqrt(s) NET ● Analysis improvements – E/B Separation – Matrix-based analysis toward map release ● Systematic error investigation example: beam differential pointing

3-Year Map More Sensitive than Anything Before E-modes Sensitivity to Q/U = 119 nK*deg. and effective area of 388 sq. deg. uK Dec. (deg.) 16 uK*sqrt(s) NET Map from Angiola Orlando RA (deg.)

Using “pureB” Estimator to Reduce E/B Mixing Effect ● Using K. Smith (Phys.Rev.D74:083002) ● Evaluating analysis choices (e.g. apodization) ● Exploring simulation approach to filtering effects Plot from Sarah Kernasovskiy

Simulation-based deprojection of E modes can further improve E/B separation B-modes preserved E-mode leakage ● “Standard” pseudo-Cl suppressed can reach pureB performance ● Can improve PureB # of deprojected E-mode realizations performance Standard estimator noise PureB estimator noise Ell ~ 100 power Plots from Kirit Karkare

Direction of longer-term future analysis is matrix-based ● Npix < 10 5 ● Plan to release maps, reobserving matrix, covariance matrices (signal, noise), beam profiles, and bandpass ● Enables joint analysis, optimal E/B separation ● Reobserving matrix calculated for BICEP2 Figure from Jamie Tolan

Characterize Beams with Artificial Sources ● Mast and flat mirrors allow far-field measurement ● Main beam shape beyond circularly symmetric Gaussian ● Sidelobes ● Polarization angles and efficiencies

Most important beam effect so far is differential pointing within a pair A-B offset for all detectors (x20) Difference beam of A and B polarizations Figure: Randol Aikin

Strategy for differential pointing ● Measured for each detector ● Deproject in analysis ● Simulate residual systematic error after deprojection ● Understand in lab measurements ● Make improved detectors—we are upgrading Keck Array with improved antennas

Keck Array Status ● Maps and sensitivity: 20 uK*sqrt(s) NET [2011] → 11 [2012] → 9.5 [2013] ● Improvements for 2013 season ● Beam investigation example: sidelobes and forebaffle loading ● Future plan

Keck Array Status ● Maps and sensitivity: 20 uK*sqrt(s) NET [2011] → 11 [2012] → 9.5 [2013] ● Improvements for 2013 season ● Beam investigation example: sidelobes and forebaffle loading ● Future plan

Keck 2012 maps are as deep as 2 years of BICEP2 Keck Array 1-year 150-GHz Q/U sensitivity: 170 nK-deg. for effective area 397 deg. 2 Maps from Sarah Kernasovskiy

We're improving Keck every year Improvement of A-B mismatch ● 2011: 3 receivers at 150 GHz (2 with HWP) BICEP2 ● 2012: 5 receivers at 150 GHz (no HWP) ● 2013: Replaced 2.25 focal planes to improve sensitivity and A-B mismatch Keck 2013 Figure: Chin Lin Wong

Dramatically improved A/B pointing mismatch Figure from Roger O'Brient

Keck is losing significant sensitivity to forebaffle loading ● Forebaffle on/off test found 0.5 pW (4 K) change in load power ● Possible 8% NET improvement (confirmed with reflective forebaffle measurement) Change in loading (pW) In-lab Forebaffle simulator Figure from Sarah Kernasovskiy

Keck far-sidelobe beam mapping found something related ● Large angle beam maps with forebaffles off ● Arc/ring sidelobe features found 20~30 deg. from main beam in many detectors ● Believed to be due to reflections from Beam map without forebaffles incompletely blackened telescope walls ● Terminate at warm baffle → excess loading

Sidelobe Treatment Plan ● In-lab verification of cause ● Improve telescopes at Pole for next season (probably with additional baffles at 4 K) Figure from Samuel Harrison

Keck Array is going to get even better ● Observation funded through 2016 ● Upgrade up to 3 focal planes for 2014 season ● Considering switching some to 100/220 GHz – Mature 100-GHz design proven by SPIDER – 220-GHz in development